In a small saucepan, combine sliced strawberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until strawberries release their juices and mixture begins to simmer, about 5 minutes. Stir in cornstarch slurry and cook for 1 more minute until slightly thickened. Remove from heat and set aside.

Preheat your waffle iron according to manufacturer's instructions. Lightly grease with nonstick spray or melted butter.

In a large bowl, whisk together flour, sugar, baking powder, and salt until well combined.

In a separate bowl, whisk together milk, melted butter, eggs, and vanilla extract until smooth.

Pour the wet ingredients into the dry ingredients and stir gently with a spatula until just combined. Do not overmix; a few lumps are okay. Fold in the diced strawberries gently.

Pour about 1/2 to 3/4 cup of batter onto the center of the preheated waffle iron (amount depends on your iron size). Close the lid and cook until golden brown and crisp, about 4-5 minutes. Repeat with remaining batter.

Stack waffles on a plate, top with warm strawberry sauce, fresh sliced strawberries, a dollop of whipped cream, and a dusting of powdered sugar. Garnish with mint if desired. Serve immediately.